Best Candidates For Pre-Columbian American Colonization

My money is on the Vikings, who actually tried it in parts of Newfoundland, but who else might have gotten here first?
 
It's not much Pre-Columbian, but the Portuguese easily could have made it earlier than they did (OTL Cabral "discovered" Brazil in 1500, but da Gama had already made it to India by that point, so Brazilian rainforest was less of a priority). If they had encountered Brazil earlier, they might have set up trading posts as they did throughout Africa, and gone on from there.
 
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